利用雷射剝離製程提升氮化鎵微型發光二極體之效能與分析

Abstract

本論文主旨為改善氮化鎵微型發光二極體 (micro-LED) 之效能，並成功研製100x100陣列數藍光micro-LED，每顆像素大小為10微米，像素中心至中心距離為12.8微米。未來期望能結合主動式驅動背板，應用於微顯示器 (micro-display) 如AR/VR眼鏡。 在成熟微形發光二極體製程中常利用覆晶封裝 (flip-chip bonding) 結合控制電路，改善藍寶石基板的低導熱與導電特性，然而覆晶封裝之micro-LED結構是從藍寶石基板(Sapphire)面出光，而GaN (n=2.4) 相對Sapphire (n=1.77) 有較高之折射率，光在傳播途徑將折射並發散，造成pixel間嚴重光互擾，因此當微型發光二極體用於顯示用途時，Sapphire勢必得移除或磨薄至一定厚度。本論文提出以雷射剝離技術 (Laser lift-off，LLO)解決光互擾問題，利用覆晶封裝搭配LLO製程去除藍寶石基板，並填入底部填充劑減少LLO造成之缺陷。

In this thesis, the major goal is to improve the characteristics of mature GaN-based micro-light-emitting diodes (μLEDs). The blue light μLEDs were successfully fabricated with the dimensions of each pixel is 10 μm, the pitch of micro-LED array is 12.8 μm, and the number of an array is 100 x 100. By integrating with active-matrix backplane, advanced applications in micro-display, such as augmented reality (AR) and virtual reality (VR) glasses can be realized through micro-LED in the near future. In mature μLEDs fabrication process, flip-chip bonding is applied to not only integrate μLEDs with backplane but also improve the thermal and electrical properties of sapphire. Since the light is emitted from the sapphire side, the large thickness of sapphire leads to light refraction and divergence because of different refractive index between sapphire (n=1.77) and GaN (n=2.4), causing optical crosstalk in adjacent pixels. Therefore, polishing or removal of sapphire is necessary with increasing density of micro-LED array for display applications of μLEDs. In this study, we propose a possible method to solve the crosstalk problem. After flip-chip bonding, Laser lift-off (LLO) process is used to remove the sapphire substrate and the underfill dispensing is applied to reduce defects caused by LLO.